Induced Cervical Dilation in Sheep: Evaluation of the Effects On
fertilization Rates and Embryonic Development

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Abstract

Experiments were conducted to determine the effects of a treatment used to dilate the
cervix for transcervical AI and embryo transfer on pregnancy or fertilization rates in sheep.
Experiment 1 was conducted as a 2 x 2 factorial, with the main effects of estradiol-17b (E2) and
oxytocin (OT). On d 6 of pregnancy, ewes received (i.v.) 100 mg of estradiol-17b, or saline; 10 h
later, ewes received (i.v.) 400 USP units (20 mL) or saline. Blood samples were collected for
progesterone analysis. Transrectal ultrasonography was used to determine pregnancy on d 25.
Treatment did not affect (c 2 , P > .05) pregnancy rates. For nonpregnant ewes, the
period Ã E2 Ã OT interaction (P < .01) was significant.
Experiments were conducted to evaluate the effects of oxytocin and(or) cervical manipulation on fertilization rates. In Exp. 2, nulliparous ewes were
assigned to one of two randomized treatment groups: 1) saline or 2) oxytocin. In Exp. 3, multiparous ewes were assigned to one of two randomized treatment groups: 1) saline-cervical
manipulation or 2) oxytocin-cervical manipulation. Ewes in Exp. 2 and 3 were laparoscopically
inseminated. In Exp. 2 and 3, ewes received (i.v.) either 400 USP units of oxytocin or 20 mL of
saline. In Exp. 2 and 3, oocytes and(or) embryos were collected. Treatment did not affect
recovery, fertilization, or pregnancy rates in Exp.2 and 3. In conclusion, the treatment used to
dilate the cervix in ewes to facilitate the transcervical AI or ET does not seem to affect
fertilization or pregnancy rates.